The present invention relates generally to control systems for internal combustion engines, and more particularly, to an electronic throttle idle speed control system.
Many previously known motor vehicle throttle controls have a direct physical linkage between an accelerator pedal and the throttle so that the throttle plate is pulled open by the accelerator cable as the driver depresses the pedal. The direct mechanical linkage includes a biasing force that defaults the linkage to a reduced operating position, in a manner consistent with regulations. Nevertheless, such mechanisms are often simple and unable to adapt fuel consumption efficiency to changing traveling conditions, and add significant weight and components to the motor vehicle.
An alternative control for improving throttle control and the precise introduction of fuel air mixtures into the engine cylinders is provided by electronic throttle controls. The electronic throttle control includes a throttle control unit that positions the throttle plate by an actuator controlled by a microprocessor based on the current operating state determined by sensors. The processors are often included as part of a powertrain electronic control that can adjust the fuel air intake and ignition in response to changing conditions of vehicle operation as well as operator control. Protection may be provided so that an electronic system does not misread or misdirect the control and so that unintended operation is avoided when portions of the electronic control suffer a failure.
For controller simplicity, a single controller structure for all ranges and modes of operation is desired. However, the plant under control (throttle actuator) has high coulomb friction torque relative to its inertia and motor torque. This results in long times from command to 90% of final value for small command changes. Unfortunately, times need to be small for good idle speed control. These times can be improved by increasing the gains, but results in adding overshoot. While in some cases beneficial, overshoot, in general, will cause the throttle mechanism to strike the stops, which can cause mechanism failure or require significant and costly added robustness to the mechanism.
The disadvantages associated with these conventional electronic throttle idle control techniques have made it apparent that a new technique for electronic throttle idle control is needed. The new technique should have short times from command to 90% of final value for small command changes. Additionally, the new technique should not cause mechanism failure or require significant and costly added robustness to the mechanism. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable electronic throttle idle speed control system. Another object of the invention is to have short times from command to 90% of final value for small command changes.
In accordance with the objects of this invention, an electronic throttle idle speed control system is provided. In one embodiment of the invention, a method for controlling a positioning device of an internal combustion engine includes the steps of: providing an electric motor for actuating the positioning device; detecting a position of the positioning device in relationship to a stop; determining whether the positioning device is near the stop; enabling overshoot when the positioning device is not near the stop; determining a velocity of the positioning device; and, enabling overshoot of the positioning device when the positioning device is near the stop, but the velocity is below a predetermined value.
The present invention thus achieves an improved electronic throttle idle speed control system. The present invention is advantageous in that will not cause mechanism failure or require significant and costly added robustness to the mechanism.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.